Tyson Foods Inc. unleashed a $6.1 billion bid for Hillshire Brands Co., the maker of Jimmy Dean sausage and Ball Park hot dogs, setting up a heavyweight battle with Brazilian rival JBS SA for one of the juiciest remaining assets in the meat industry.

The all-cash bid on Thursday came two days after JBS's Pilgrim's Pride Corp. made an unsolicited offer for Hillshire that valued it around $5.5 billion. Either bid for Hillshire, if successful, would mark the meat-industry's biggest merger, according to data provider Dealogic....